Not every project needs a grading and drainage plan, but some do. Before moving any dirt for a project, ask the Public Works or Engineering Department for your local jurisdiction (i.e., City, Town, County) whether you need a grading permit. This will ensure that you avoid fines or fees associated with neglecting to obtain necessary permits. A grading and drainage plan is often required to acquire a grading permit. This is important because building permits may not be issued until the Building Inspector approves rough grading. In the following blog post, I will describe the elements of a grading plan and discuss who can prepare grading plans.

What is a grading plan?

In short, grading is the movement of dirt used to sculpt the ground into the shape necessary for the aesthetic appeal and drainage conditions required for a particular project, development, or subdivision. A grading plan is part of a construction drawing set that describes the earthworks activities that will be conducted as part of the construction of a project. As such, the grading plan will show design elevations, swale locations, and dimensions of water features such as ponds, and drainage patterns. A drainage plan outlines the existing and proposed downspouts, pipes, catch basins, etc. Although a drainage plan or drainage site plan may be prepared separately from the grading plan in some cases, they are most often combined into a “grading and drainage plan.”

Landscape grading involves sculpting the land to direct water away from buildings and other structures. A lot grading plan specifies the pad elevation, lot type, and surface gradient for each home within a land development project.

Who needs a grading plan?

Typically, grading that involves moving at least 50 cubic yards (CY) of dirt will warrant some sort of grading permit. Sometimes the project architect or landscape architect can prepare the grading plan for smaller projects. However, grading that involves moving 500 CY or grading that will support a structure needs to be performed per a grading plan prepared by a licensed civil engineer.

What is needed to prepare a grading plan?

To begin preparing a grading and drainage plan, the civil engineer will need a topographic survey, site plan, and soils report. These elements are discussed in more detail below.

Topographic Survey

A topographic survey prepared by a professional licensed surveyor (PLS) is required to generate a stamped grading and drainage plan for an engineering project. The survey should include the property line/boundaries as well as topographic information. It is also important to make sure the surveyor provides CAD files in addition to a PDF of the survey information.

Site Plan

In addition to the survey, the civil engineer will need the site plan to prepare the topographic survey. The site plan shows the location of proposed proposed features such as parking lots, landscaped areas, buildings, etc. The site plan should be properly scaled and provided as a CAD file. Ideally, the architect should overlay the site plan on top of the topographic survey.

Soils Report

In California, a soils report is typically required for projects that require grading. The soils report will discuss over-excavation and other information pertinent to grading. The soils engineer also typically needs to sign off on the grading and drainage plan before excavation can begin. If you will install an infiltration/retention feature to meet the stormwater requirements for your project, I recommend requesting that the soils engineer perform a percolation test. This test will determine whether the soil will drain quickly enough for a retention feature.

How is a grading plan generated?

A grading plan is typically generated using computer-aided design (CAD) software. The benefit of programs such as AutoCAD Civil 3D is that they allow users to design and draft simultaneously.

What information is included on a grading plan?

Grading plans show contours, spot elevations, slopes, and other information that depict the proposed design. In addition, grading plans may include other clarifying information such as sections and details. Finally, grading plans typically include earthwork quantities (cut and fill). This information is generally used to file the grading permit. It is worth noting that grading plan requirements differ by jurisdiction. Some cities and counties have specific information related to the notes included on the plan or how the plans should appear.

What is an erosion and sediment control plan?

An erosion and sediment control plan is often prepared along with the grading plan. It shows the measures that will be taken during construction to ensure runoff, dirt, and other construction waste from the project will not contaminate local streams or the surrounding properties/neighborhoods.

Site Grading Terminology

The following list defines some terms commonly used in grading plan preparation.

Backfill – a term to describe the material used to refill an excavated hole or trench.

Berm – a raised piece of land or mound of soil placed to divert water away from a structure or feature.

Borrow Pit – an area used to remove earth that will be used for fill material in another location.

CAD – Computer Aided Design (CAD) software used to draft construction plans. Some examples of CAD programs include AutoCAD (most common), MicroStation, and BricsCAD.

Contour – A line that indicates areas of the same elevation. Contours are typically shown at one-foot intervals for land development projects. Existing contour lines are often depicted in a lighter color and are dashed. In contrast, proposed contour lines are typically darker in color and are typically solid lines.

Cut and Fill – Earthwork that is to excavated is referred to as “cut” while excavated material that is placed is referred to as “fill.”

Easement – An area or property designated for a particular purpose (e.g., power easement, sewer easement)

Existing Grade – The elevation of the ground surface before any earthwork activity.

Fine Grading/Finish Grading – Fine grading, which is also referred to as finish grading, is performed after rough grading and ensures that the ground surface elevations match what is shown on the construction plans as closely as possible.

Final Grade – The elevation of the proposed ground surface.

Limit of Disturbance (LOD) – A boundary line that shows the point at which the proposed contours meet the existing contours. Areas outside of the LOD should not be touched. The area within the LOD is important for permitting purposes. For example, a disturbed area greater than one acre will require a SWPPP.

Profile – A profile depicts elevations along an alignment (which is often the center of a channel, stream, or road). Profiles are typically provided for storm drains, channels, retaining walls, bank protection, or roads. An example of a profile view is shown below. Typically, profiles are presented above the plan view.

Proposed Conditions – The designed condition.

Retaining Wall – A rigid wall that supports soil laterally. In general, retaining walls that are 4 feet in height or smaller can be designed by a civil engineer with little to no geotechnical analyses. However, larger retaining walls require the consultation of a licensed structural or geotechnical engineer.

Rough Grading – Earthwork activities that involve excavating the general shapes and slopes shown on the grading plan. In this way, rough grading could be considered a “first pass” towards achieving the elevations shown on the grading plan.

Section – A section will show a cross-sectional view of the proposed ground surface. A section includes relevant dimensions and elevations. Sections are typically shown for stormwater features and highway projects. An example of a section is shown below.

Setback – the minimum distance which a building or other structure must be from a road, stream, floodplain, or any other place which is deemed to need protection.

Stationing –

Swale – an open channel that conveys flow.

Slope – the amount of vertical change over a certain horizontal distance. It is often calculated as rise/run. On grading plans, the longitudinal slope is usually expressed as a percentage, and side slopes are usually expressed as horizontal: vertical (H: V).

Spot Elevation – Spot elevations, which are also called spot grades, refer to the exact elevation at a particular point. Typically, spot elevations are reported to the nearest hundredth (0.01) of a foot. An example of a spot elevation is shown below.

Survey – A topographic survey, which is often referred to as the “survey,” is performed before preparing a grading plan. The survey depicts the existing condition of the site and includes the following information: existing elevations/contour lines, location of existing structures, location of existing trees and vegetation, and the location of existing utilities. The survey should also include boundary or property line information.